String literals are const char*.

GCC won't whine with -Wall because so much code isn't const correct but
writing to a string literal is undefined. -Wwrite-strings is the warning
flag to enable to spot these.
diff --git a/docs/contributing.rst b/docs/contributing.rst
index 63c9953..657c435 100644
--- a/docs/contributing.rst
+++ b/docs/contributing.rst
@@ -141,17 +141,17 @@
 
 .. code-block:: c
 
-    #define SOME_INTEGER 0x0;
-    #define SOME_UINTEGER (unsigned int)0x0001;
-    #define SOME_STRING "hello";
+    #define SOME_INTEGER_LITERAL 0x0;
+    #define SOME_UNSIGNED_INTEGER_LITERAL 0x0001U;
+    #define SOME_STRING_LITERAL "hello";
 
 ...it should be added to the bindings like so:
 
 .. code-block:: c
 
-    static const int SOME_INTEGER;
-    static const unsigned int SOME_UINTEGER;
-    static char *const SOME_STRING;
+    static const int SOME_INTEGER_LITERAL;
+    static const unsigned int SOME_UNSIGNED_INTEGER_LITERAL;
+    static const char *const SOME_STRING_LITERAL;
 
 Documentation
 -------------